(a) Field of the Invention
The present invention relates to a wireless personal area network, a coordinator thereof, and a coordinator selection method for hand-over thereof. More specifically, the present invention relates to a wireless personal network in which a candidate device for performing as a coordinator participates in a communication performance test, a coordinator thereof, and a coordinator selection method for handover of the coordinator.
(b) Description of the Related Art
A wireless personal area network, specifically a piconet, is a collection of devices using the same physical channel for interchanging information. When a piconet is formed, one device acts as the master, which is called a piconet coordinator, for generating a beacon and managing the network, and common devices for interchanging information under control of the piconet coordinator act under the control of the piconet coordinator.
Coordinator hand-over is performed when a new device for performing a role as the coordinator participates in the network, and the new device performs better than the coordinator that is currently used. The role as the coordinator is transferred to a device having a best performance by comparing functions of devices in the network when the coordinator currently used leaves the network or stops operating. At this time, selecting a coordinator by comparing the functions of devices in the network is called coordinator selection.
A coordinator has been conventionally selected by simply comparing information on functions (e.g. transmission power and maximum number of devices that are able to be controlled) of devices. A device may not perform as a coordinator even though the function of the device is great because the communication performance between the devices is not considered when the coordinator is selected when simply comparing the functions of the devices. Accordingly, a configuration inquiry method is used to solve the above problem. In the method, communication performance between the devices is considered.
The configuration inquiry process comprises: a first step in which the coordinator broadcasts a configuration inquiry (CI) request command, and the device having received the CI request command broadcasts a CI response command in order to inquire of the communication performance, and other devices receive the CI response command and store a transmission device ID in an accessible device list; a second step in which each device broadcasts the information on the accessible device list included in the CI response command to the coordinator in order to inform the accessible device list, and the coordinator that receives the command stores the information; and a third step in which the coordinator broadcasts a CI terminate command to stop the CI process with devices in the network.
The CI process has problems as follows.
First, the test for the communication performance among devices is performed in one direction, because the communication performance is inquired by transmitting the CI response command in the second step. Therefore an accessible state may be determined when communication between devices is not performed.
Second, a coordinator selection process is performed when a coordinator hand-over is performed, and therefore it is difficult to immediately transfer a coordinator role when it is urgent.
Third, messages for a communication performance test may be excessively generated because all devices participate in the test.